What Happens To All the Universe's Hydrogen?

StartsWithABang (3485481) writes "Just a second after the Big Bang, the Universe was a hot bath of radiation, with a small fraction of protons and neutrons in about equal numbers left over. By time it was four minutes old, it was 92% hydrogen (by number of atoms) and 8% helium. Yet the Universe has aged nearly 14 billion years since then, and have formed many generations of stars, all of which burn hydrogen into heavier elements. So how much hydrogen is left, and how much will be left far into the future? A lot more than you might think."

Comments

Re:So, um, only protons and neutrons?

[rossdee]

So the universe was positively charged? I think theres a mistake somewhere.

Survivalist

[theshowmecanuck]

I'm keeping a two year supply in my basement.

Re:Survivalist

[Thanshin]

Well yeah. You know, in case he needs water, RIGHT NOW.

Re:Survivalist

[theshowmecanuck]

Solider metal.

Re:Ahhhhhh

[Tablizer]

No, that's methane. Wrong gas.

Re:Ahhhhhh

[Cryacin]

Well, at least we know that a significant amount of CO2 gas has been successfully sequestered in that article.

And what about dark matter?

[1 a bee]

I'm a bit skeptical of such cosmological estimates. If there is more dark matter in the universe than ordinary matter (by a factor of 4:1 they say), wouldn't you expect it to somehow figure in the "calculations" going back to the big bang? I saw no mention of it in the article. In fact, come to think of it, you seldom hear much about that big elephant dark matter in the room in the first minutes after the bing bag.

Love reading about cosmology, but I think readers should be warned this is a very speculative field of study. Ideas and models in vogue today will likely not be in a few decades. I'm reminded of my physics professor of many years ago who claimed "Cosmology is as mature as botany was before Darwin."

Re:And what about dark matter?

[boristhespider]

Eh?

"If there is more dark matter in the universe than ordinary matter (by a factor of 4:1 they say), wouldn't you expect it to somehow figure in the "calculations" going back to the big bang?"

Yes. And yes, it does, it "figures" right from the start.

"I saw no mention of it in the article."

Who died and made this article God?

"In fact, come to think of it, you seldom hear much about that big elephant dark matter in the room in the first minutes after the bing bag."

That's chiefly becase in the first few minutes after the big bang the universe was radiation dominated, meaning that the density of photons (and neutrinos) was vastly greater than that of dark and normal matter. The transition between radiation and matter domination is governed by the density of dark matter just as much as baryons. Where on Earth are you getting this idea that dark matter is an "elephant in the room"? Here's an interesting fact for you - you know there are waves imprinted both on the CMB and on the large-scale structure of galaxies, right? If you "love reading about cosmology" you must, right? Those waves are the result of oscillations while the universe was radiation-dominated, caused by baryons tending to cluster together under gravity, and a restoring force introduced by radiation pressure, which set up ringing oscillations across the universe. Without dark matter to provide extra clustering under gravity those waves are at totally the wrong wavelength. From the CMB *alone* you can find how much dark matter there has to be relative to normal matter. How's that for an "elephant in the room"?

"I think readers should be warned this is a very speculative field of study."

As is all theory. However, I think readers should be warned that the fundamentals of cosmology are very far from speculative - even if the results might in principle be phenomenological, they will not change. Cosmology, particularly in the early universe but after the first microsecond, say, is based on well-understood science and is anything *but* speculative, and questions about whether dark matter or dark energy are physical quantities or are emergent in one way or another are not unique to cosmology but also arise on astrophysical scales. (And in some ways are irrelevant, since whatever dark matter and dark energy actually are, they have to work as cosmology describes them anyway. Small changes to the Lambda CDM model cause large disagreements with the data.)

"I'm reminded of my physics professor of many years ago who claimed "Cosmology is as mature as botany was before Darwin." "

Err, yeah. How many years ago? If he held the same opinion now I'd be surprised. If he held that opinion after the late 90s then he was ignorant of the field. That's OK, my Masters supervisor, in the early 2000s, is a brilliant physicist and held a similar opinion (although not stated quite so... badly, with a lousy analogy that could never work), and he was wrong too, increasingly so as the datasets grow ever huger and the tools with which to analyse them evermore sophisticated. This kind of view is untenable, and I say that as a man who has gone on record repeatedly with statements such as "cosmology is wrong. It is demonstrably wrong, it is wrong in its fundamentals and it is wrong in its principles" - because that's a statement I also surround with caveats. Cosmology is "wrong" in the same way that thermodynamics is "wrong", or that much of chemistry is "wrong", or much of biology is "wrong", in that it's at heart a descriptive, phenomenological theory. (Before chemists or biologists come to me to scream, those fields are typically phenomenological, although both contain subfields that are avowedly not so; but ultimately if you're not mapping up from the behaviour of the individual atoms you're dealing with phenomenology, and I'm well aware of how brutally difficult it is to do chemistry directly from the Schroedinger equation, which is what that implies. 'Phenomenology' is not a criticism, unless it's taken as so by people who mistakenly think they're dealing with the underlying science directly.)

Re:And what about dark matter?

[boristhespider]

Time, yes. Not sure what you're referring to with thermodynamics - it's just a statistical theory that emerges when you deal with vast numbers of particles. (And if I did want to treat thermodynamics as inviolate, which it basically is for large enough systems of particles, there is no issue with conservation of energy with the loss of energy due to cosmological expansion. I'm not totally sure why you'd think there is: energy conservation is inherent in the system. There's nothing controversial about the idea that if you work in an expanding spacetime then photons that are not being pumped by an external source of energy will be stretched. Similarly if you work in a collapsing spacetime then photons not being drained with be blue-shifted. The Friedmann equation can ultimately be interpreted as an energy conservation equation if one is so minded, it just comes from the Hamiltonian constraint.)

Re:And what about dark matter?

[meta-monkey]

The problem with the new Cosmos is not all the "facts" they present are scientific. They also deal with history, and some of their "facts" are misleading or downright wrong, and we don't apply the scientific method to history.

I get that Seth MacFarlane is an atheist and wants to push his creed (or lack thereof) on people. But in the first episode of Cosmos, the whole story about Bruno and his persecution was just wrong. Yes, Bruno did have an idea that the universe was infinite and that the sun was just another star. But he was not a scientist, did not apply the scientific method and did not back up his ideas with experiment or observation. He was "right" in the same way a broken clock is right twice a day. He was a mystic who wrote books about magic and thought the stars and planets had souls. While no one should be burned at the stake for any reason, he was not killed because of his scientific views, he was burned because of his religious heresies like denying the divinity of Christ. The bit went on for about 8 minutes of airtime, in a 40 minute show. They spent 20% of a science show talking about the persecution of a religious man for his religious views but making it out as if he were persecuted for his scientific practice, when he wasn't. It was purely a shot at religion in general and the Catholic Church in particular in order to push MacFarlane's world view. I thought they sacrificed their credibility by intentionally misleading people about historical facts.

When my kid is old enough to understand Cosmos, I'll be showing him Sagan's version. Little has changed with regards to the history of science since the original Cosmos and now, and Carl wasn't pushing an agenda. He was just giving you facts. Also, CGI not withstanding, I thought the production values of the original were better. I like the way they hired actors to portray famous moments in science rather than Neil's version with cartoons to depict past events.

Re:And what about dark matter?

[rgbatduke]

Well said, sir. Repeatedly, even. Although (as a physicist also) I do have to say that DM/DE are a) one of several possible explanations or models that we have -- so far -- and while it has emerged as one of the most consistent that doesn't make it either unique or right. We may not have even hypothesized the right model yet (given the indirect nature of the data, that would hardly even be surprising, if true). b) One of the problems with having a huge amount of mass-energy out there, effectively decoupled to electromagnetic forces, in addition to making said mass-energy literally invisible is that one can imagine entire "universes" of field theories underneath the very loose constraint of the observational data. Does DM couple to e.g. the nuclear force? Are the quanta of DM stable? Is DM not really "dark", but merely very, very weakly interacting, e.g. massive neutrinos? IIRC it is possible to explain the cosmological data by giving three flavors of neutrinos a mass-energy order of an eV. And then we have to ask -- what if there are more than three flavors, and DM is a "leftover" neutrino from a super-heavy lepton that hasn't existed since the big bang so that the neutrinos have nowhere to go? DE is even more difficult to cope with -- are we talking about the massless quantum of a fifth force altogether, or is it somehow tied to the four fields we already know about?

Given that we have yet to fully reconcile gravitation and relativity in a consistent quantum theory and that we lack a TOE (meaning there is still room enough to drive -- err, "elephants" through the gaps:-) we are, as you say, working with descriptive phenomenology -- classical theories of gravitation, or relativistic theories of curved spacetime, quantum models of nuclear (strong and weak) and electromagnetic interactions that works (so far) pretty well in specific contexts. But we don't even know if DM interacts strongly enough with sufficiently dense "known" matter -- matter e.g. in the heart of suns -- to be able to slow down in transit and accumulate. We don't know if DM remains stable and decoupled at energy densities like those accessible inside the cores of stars, or for that matter inside e.g. neutron stars. We don't know if DM interacts with other DM to be able to provide the "friction" needed to cause gravitational collapse of DM. All we know is that when we examine galaxies, the profile of orbital velocities observed is consistent with their being more matter in the galaxy than we can see, distributed in a very unusual way.

Personally, I think it is all very interesting (although definitely not my field), but don't take any of the many assertions about DM or DE too seriously yet. Both are the ultimate "invisible fairy theory" -- literally invisible -- where the fairy is known only indirectly by means of the "the fairy must have done it" argument. This is right up there at the edge of religious thinking, because as long as the fairies remain invisible, it remains almost impossible to falsify any assertion about what the fairies do or do not cause in the observational data. I'd mumble about Ptolomeic epicycles vs gravitation, or the many gods of the many gaps over human history, but in the end, until somebody puts salt on the tail of a darkon or manages to build a TOE that includes DM/DE consistently, explains all observations, and has a prayer of being verified/falsified by more than crude phenomenological agreement it is all in the same category as supersymmetry, string theory, etc -- pretty stories, but which one (if any) of the myriad of possible models within the general approach is true?

rgb

Re:Ahhhhhh

[donaldm]

No, that's methane. Wrong gas.

I realise the AC was making an off colour joke but the chemical symbol of Methane is CH4 so it does have hydrogen in its chemical formula.

Re:Ejected hydrogen

[davester666]

Great. Now I have to search for the porn video of this.

Re:So, um, only protons and neutrons?

[flyingfsck]

That must be why the big bang happened - all charged up and nowhere to go.

Re:Thought experiment

[flyingfsck]

Bugger all is gonna happen to your infinite number of balloons, unless you have an infinite amount of oxygen too.

Re:I was wondering this myself...

[Blaskowicz]

Hydrogen cars are a scam. H2 has a great energy density by mass, but a very poor energy density by volume. You need very high pressure storage in a tank.. Heavy, expensive and the hydrogen consistently "wants" to leak out, being so thin.
Or you need liquid hydrogen, which needs a non trivial cryogenic apparatus. A non-starter, not even all launch rockets use liquid hydrogen.

In the end, hydrogen needs to be bound back to other atoms to be a usable fuel for transportation, some promising uses for H2 could be to manufacture CH4 using CO2 from a cement factory, or NH3 using nitrogen from air. But this consumes further energy, which would need to come from a mix of solar thermal, renewable electricity and nuclear from the grid.

Where does the H2 come? There's water electrolysis, which needs a ton of electricity. High tech schemes for cracking water into H2 and O2, using concentrated sunlight and whatever.. I don't know how's that going. And of course, the cheaper way that has actually been done on a massive scale for decades, extract hydrogen from natural gas (if you want to, that can be done from coal ultimately). That's vastly cheaper, and going through the pain of producing hydrogen that way, liquifying it for mass storage, getting it in some form in cars and burning it would make no sense at all next to just burning natural gas in cars.

Re:I was wondering this myself...

[Sockatume]

You don't burn hydrogen in a hydrogen vehicle. You use it to run a fuel cell which, being electrochemical, doesn't have the Carnot limit on its efficiency. So even a relatively inefficient hydrogen cycle can actually be better than making liquid fuels for an internal combustion engine. The challenge, as you say, is engineering a good hydrogen storage material. (The chemistry problems involved in the efficient photolysis of water are related to the ones involved in the efficient photocatalytic production of liquid fuels, so the research on each side tends to assist the other.)

On the gripping hand, fast-fuelling long-range vehicles are an artefact of cheap, readily available gasoline rather than an inherent part of the human condition so I can't see them being competitive with modest-range battery vehicles in the long term.

Re:helium

[oodaloop]

There's plenty on the sun we can mine. A bigger problem, though, is the dwindling vacuum supply. We need to get into space and start mining vacuum.

Re:And I stopped when

[OakDragon]

And here he is, high as fuck.